DACS that isolate well.

[Superdad]

4 hours ago, beerandmusic said:

I was wondering if anyone knows of an inexpensive DAC that pays special attention to isolating well, that also provides it's own 5V reference voltage for the usb, and that reclocks. I don't want to get into the debate whether noise matters or not....just looking for a few different models that do this well. I already heard that the D90 does not have galvanic isolation...and i don't know about the other 2 features I want (provide their own 5v ref and reclocks).

I know the Schiits unison advertises it does this (galvanic isolation, reclock/regenerate, and provide their own 5v reference)

 

Sorry, but you mis-understand both clocking and digital isolation.

 

All DACs "reclock";

You are confusing DAC audio-rate clocking (22.5792MHz/24.576MHz and multiples thereof) with the data clocks for interface chips (e.g. 24.00MHz or 25.00MHz).

[And by the way, despite anyone's marketing--including my own--"regenerate" is technically a meaningless thing.  USB (and Ethernet) data has to pass through both a PHY and a MAC (medium access control) protocol processor (these days the former is generally integrated into the latter). You could call the passing through any MAC a "regeneration" of the signal. (The term "regenerate"--related to USB--dates back to UpTone Audio coining it for our original USB REGEN back in 2014; Call it our "Kleenex" moment. ) We use USB hub chips--those are a form of MAC too--to "regenerate."  With any act of passing data--through a processor of any kind--some things are left behind and some things are passed through. Such is beyond the scope of my interest in this reply...

 

In regards the above, the Schiit Unison USB input board--which you mention in multiple posts--is no different. They simply chose a more open architecture microprocessor (a Microchip PIC32) to tweak their own USB handling code--as opposed to staying with the Cmedia previously used or choosing the XMOS environment. I applaud them, but the rest of what they are doing on the Unison board about the same as their prior Gen5 USB, with a Wurth Ethernet transformer module and a standard digital isolator on the I2S lines.

 

No DACs (except for Auralic Vega G2 and Phasure NOS1a which both use the no-longer-available Silanna ICE08USB high-speed USB isolator--as also used in our ISO REGEN) have digital isolators BEFORE their USB input stage; Any DAC or DDC that you see advertising "galvanic isolation" of their USB (or Ethernet) input are doing so with digital isolators on the I2S lines--AFTER the USB input stage.  [That is because USB is a bi-directional protocol on a single pair of data wires and ALL digital isolator chips pass data in only one direction (yes, many isolators have more than one bit channel in the same package and one can choose the combination of directions; but that does not make them bi-directional). The USB protocol reverses data flow on a single wire pair.]

 

You also mention wanting a DAC that "provides its own 5V reference." I am sure you mean one that does not rely on USB 5VBUS power for its input stage. But unless a DAC designer goes to the trouble and expense of building in an entirely separate power supply just for the USB>I2S input board (and I mean if not a separate power transformer, at least a dedicated transformer secondary, separate set of AC>DC rectifying diodes, and voltage regulators--all to keep a separate 0-volt/-VE "ground" reference), your requirement will be at odds with having digital isolator chips on the I2S lines after said USB input stage.